NATURAL PHILOSOPHY. 177 



tion of Kepler and others may have been, it was clear that a force like 

 that of magnetism would not be able to transact the business of the uni- 

 verse. 



The object of the evening's discourse was to inquire whether the force of 

 diamagnctism, which manifested itself as a repulsion of certain bodies by the 

 poles of a magnet, was to be ranged as a polar force, beside that of magne- 

 tism ; or as an unpolar force, beside that of gravitation. 



Bv means of a beautifully-devised piece of apparatus, which cannot well 

 be explained without a diagram, Prof. Tyndall was enabled to experiment- 

 ally prove that the force of diamagnetism was a polar force, precisely an- 

 tithetical to the force of magnetism. The diamagnetic substance operated 

 on in the first instance, was bismuth, but the same action was found to take 

 place with various other substances, as phosphorus, nitre, sulphur, calcareous 

 spar, statuary marble, etc., each of these substances was proved polar, the 

 disposition of the force being the same as that of bismuth and the reverse 

 of that of iron. When a bar of iron is set erect, its lower end is known to 

 be a north pole, and its upper end a south pole, in virtue of the earth's in- 

 duction. A marble statue, on the contrary, has its feet a south pole, and its 

 head a north pole, and there is no doubt that the same remark applies to its 

 living archetype ; each man walking over the earth's surface is a true diamag- 

 net, with its poles the reverse of those of a mass of magnetic matter of the 

 same shape and in a similar position. 



OX THE COXSEEVATIS3I OF FORCE. 



The following lecture by Prof. Faraday, before the Royal Institution, is 

 one of the most interesting contributions made to physical science during the 

 past year. The reputation and experience of the author, the interest felt by 

 all scientific men in his communications, and the fact that the paper has not 

 hitherto been republished in the United States, are reasons for its entire re- 

 production in the pages of the Annual of Scientific Discovery. EDITOR. 



Various circumstances induce me at the present moment to put forth a 

 consideration regarding the conservation of force. I do not suppose that I 

 can utter any truth respecting it that has not already presented itself to the 

 high and piercing intellects which move within the exalted regions of science ; 

 but the course of my own investigations and views makes me think that the 

 consideration may be of service to those persevering laborers (amongst .whom 

 I endeavor to class myself) who, occupied in the comparison of physical 

 ideas with fundamental principles, and continually sustaining and aiding 

 themselves by experiment and observation, delight to labor for the advance 

 of natural knowledge, and strive to follow it into undiscovered regions. 



There is no question which lies closer to the root of all physical knowledge 

 than that which inquires whether force can be destroyed or not. The pro- 

 gress of the strict science of modern times has tended more and more to 

 produce the conviction that " force can neither be created nor destroyed ; " 

 and to render daily more manifest the value of the knowledge of that truth 



/ 



in n xperimental research. To admit, indeed, that force may be destructible 



